The present invention relates to a pattern forming method using a charged particle beam process, and a charged particle beam processing system and, more specifically, to a pattern forming method using a charged particle beam process and suitable for preventing the corrosion of a workpiece by a reactive gas when minutely processing the workpiece by using a charged particle beam and the reactive gas, and improvements in a charged particle beam processing system.
A charged particle beam, such as a focused ion beam or an electron beam, can be focused in a beam of a very small diameter. Fine processing of wiring patterns of semiconductor devices, such as LSI circuit devices, for the correction of the wiring patterns of semiconductor devices and the analysis of defects in semiconductor devices can be achieved by using the energy of a charged particle beam. Since fine processing using a charged particle beam is a sputtering process in which atoms or groups of atoms of the materials of the workpiece are caused to sputter by the impingement of the charged particle beam on the surface of the workpiece, the processing speed of the fine processing is relatively low, the selectivity of the fine processing in terms of the material of the sample, i.e., a workpiece, is relatively low, and it is very difficult to stop processing at a desired layer in a workpiece of a laminated structure having a plurality of layers of different materials.
Active studies have been made in recent years on processing techniques using a reactive gas and a charged particle beam, such as a focused ion beam or an electron beam, in combination. These processing techniques activates a reactive gas by the energy of a charged particle beam to induce a chemical reaction. Therefore, these processing techniques enables the rapid etching of a workpiece, and is capable of stopping processing at a desired layer of a material in a laminated structure by selectively using a reactive gas suitable for processing the layers of different materials of the workpiece.
A technique relating to a processing system using such a processing method is disclosed in JP-A No. 1-169860.
Although a pattern forming method (process) using, in combination, a reactive gas and a charged particle beam is capable of rapid processing, some reactive gases are highly corrosive to metals. For example, if chlorine gas (Cl.sub.2 gas) is employed as a reactive gas in processing a workpiece made of aluminum (Al), Cl.sub.2 gas adsorbed by the workpiece remains on the surface of the workpiece even if the supply of Cl.sub.2 gas is stopped. Therefore, the Cl.sub.2 gas retained on the surface of the workpiece by adsorption reacts with moisture contained in the atmosphere when the workpiece carrying the Cl.sub.2 gas is taken into the atmosphere, corrodes the Al workpiece and damages processed portions of the Al workpiece.
Nothing about the processing of the reactive gas adsorbed by the workpiece is considered by the prior art.